Time dependent behavior of FRP-strengthened RC beams subjected to preload: Experimental study and finite element modeling

This paper deals with the influence of preload and FRP stress-lagging on the time dependent behaviors of strengthened concrete beams. For this purpose, three concrete beams were fabricated: one (B1) strengthened directly without any preload; one (B2) preloaded, fully unloaded and then strengthened; one (B3) preloaded by the same value of force as B2, but strengthened with the preload remaining. Sustained loads were applied to test beams and their deformations and cracking patterns were recorded for comparison. According to the test results, B1 presented the largest long-term deformation with the most evident crack propagation in load sustained period, followed by B2 and B3. Accordingly, non-linear finite element (FE) analyses were performed. The validity and accuracy of the FE models were demonstrated by comparing theoretical and experimental results. The effect of adhesive creep was also investigated on the basis of the proposed FE approach. It could be concluded that adequate development of cracks before sustaining loads may have positive influence on better controlling the long-term deformations, while higher level of shear stress in bonding interfaces may present negative effects.